Test method description

Stent are positioned in transparent silicon tubes with thin walls. Tubes are filled with relevant test solutions depending on stent type and test requirements. A cyclic or a static differential pressure can be directly applied on the silicone tubes. The differential pressure generates a uniform periodic stress of physiologic magnitude at frequencies of up to 100 Hz. Typical tester operating mode can generate operating stress levels with peripheral pressure difference. Standard tests are performed with distilled water and under thermo regulated 37+2 °c conditions if required. Other test fluid such as saline solution can be used for biological tissue covered and biodegradable stent designs. Stent dynamic displacement and frequency is directly measured in-line by ultrasound (us) system in compliance with standard requirement and in order to ensure that dynamic amplitude levels are meeting specifications limits. Applied pressure difference, test frequency, number of cycles and stent positions within the mock artery models are monitored daily. A visual inspection is also performed daily to detect visible stent failure. Dynamic stent diameters and displacement are measured directly on the device at periodical intervals and at both the beginning and the end of the test. In order to detect early onset of failure and fracture, periodical diameter and displacement monitoring and measurement can be performed to assess stent behavior. Stent preparation, cycle counting, test frequency measurements, calibration of the pressure transducers are performed in compliance with and controlled by proper operating procedures.